Containers or cans composed of composite sheet materials are well known in the prior art. Familiar examples include the paper composite one-quart can for motor oil and the paper walled containers used for storing foodstuffs such as Parmesan cheese. Typically such composite containers have substantially flat top and bottom end pieces usually composed of metal or plastic. The one quart motor oil can, for example, conventionally has a flat metal top and bottom which are crimped to the composite cylindrical lateral sidewalls. The Parmesan cheese can usually has a flat plastic two-piece top with perforations present on a portion of the inner piece and a rotatable cover piece which provides partial coverage of the inner piece. This flat plastic top commonly is glued to the composite sidewalls.
The laminated paper composite sheet material of which the lateral walls are composed offers several advantages. The material is economical and the paper portion is derived from a renewable resource. Paper is also a biodegradable material. Therefore many modern consumers perceive laminated paper containers to be desirable for environmental reasons.
Despite these advantages, the paper composite container has been displaced in recent years for some traditional applications. For example, many one quart motor oil containers are now made entirely of plastic. The plastic containers have conical tops which function as pouring spouts eliminating the need for a separate funnel. They also have screwtop closures which permit resealing the containers after partial use of the contents, unlike flat topped containers. These considerable advantages have led to the widespread adoption of the plastic motor oil can despite the cost and biodegradability disadvantages of plastic.
In light of the advantages of a reclosable conical spout and of a container composed of paper composite material, some containers have combined the two. For example, in U.S. Pat. No. 4,848,601, Reil discloses a container having lateral walls of coated cardboard joined together in a tubular configuration and having a plastic top with a pouring spout. This pouring spout is made of a flexible material so that it may be folded down within the walls of the container during storage, and is popped up by the consumer before use. The plastic top is secured to the sidewalls of the container by a method described only as "injection along the outer rim". In this context, "injection" apparently indicates a press fit, since no other sealing step or means is described or claimed. Namba et al., in U.S. Pat. No. 4,527,699, disclose a container having a trunk member of rectangular cross section composed of a laminated sheet material having a thermally bonding synthetic resin layer on the inner surface. This trunk member is joined along one seam by overlapping the thermal resin coated inner surfaces of the two edges and thermally welding the overlapped portion. This container also has a plastic top of pyramidal shape with a screw cap closure at its apex. A flange on this top fits into the tubular trunk member. The outer surface of this flange bears a thermoplastic resin layer as does the inner surface of the trunk member. The cap and trunk are thermally welded together to provide a tight seal.
These prior art containers do not suffice for all applications in which a conical top could be joined advantageously with a composite body. For example, joining the plastic top to the composite body by "injection" or a press fit does not provide a reliable seal. This is particularly troublesome when the contents are hazardous chemicals, since spills and leakage are unacceptable. Also, the thermal bonding technique employed by Namba et al. to join the plastic cap to the composite body requires that the composite material have an innermost layer of a thermoplastic, and therefore is not adaptable to composite material bearing a non-thermoplastic innermost layer. Moreover, thermal welding is advantageous principally in large scale automated production. Accordingly, one object of the present invention is to provide a container with a paper-based laminar composite body and a conical plastic top which are securely joined without thermal welding or injection of the top onto the body.
Particular challenges are presented by a container suitable for storing and dispensing toxic chemicals such as pesticides and herbicides or petroleum based products. Such a container must be strong and impermeable to minimize the chance of accidental spills or leakage. It must resist puncture and splitting. It must also provide a strong bond between the top and the lateral walls so that the top will not break out after rough treatment such as dropping. Moreover, it must be capable of being substantially completely emptied so that residual toxic materials do not inadvertently contaminate the empty container when it is discarded. A suitable container should minimize crevices in which powdered or granular toxic materials or viscous oils and solutions may lodge. In addition, controlled dispensing of the contents would be facilitated if means were provided for pouring the toxic chemical at a controlled or restricted rate. Accordingly, it is another object of this invention to provide a container with a paper-based laminar composite body and a conical plastic top which is suitable for storing and dispensing powdered or granular toxic chemicals.